The authors investigated the predictive and incremental validity of the Early Assessment Risk List for boys (EARL-20B; Augimeri, Koegl, Webster, & Levene, 2001), a structured clinical checklist designed for the professional judgment of risk for aggressive and disruptive behaviors and risk/needs factor-based management of this risk. Seventy-six boys consecutively referred to child psychiatric outpatient clinics in mid-Sweden were evaluated according to the EARL-20B and with independent (not EARL-20B-based) clinical evaluations. The participants were prospectively followed after 6 and 30 months. EARL- 20B-based assessments were positively and moderately associated with aggressive (reactive and proactive aggression) and disruptive behavior (conduct problems and DSM-IV Conduct Disorder) at both subsequent evaluations. Clinical evaluations made without the instrument were not as consistently associated with outcome. Incremental predictive validity over unstructured clinical evaluations and Conduct Disorder at baseline suggested promising clinical utility. The checklist might be used to support clinical decision making for referred boys at risk for continued antisocial behavior.